A demultiplexer having a Mach-Zehnder interferometer of this kind is disclosed in European patent publication 0,482,461. The configuration of the two arms is defined only by the influence thereof on the wavelength-dependent or polarization-dependent optical path difference. Various possibilities with Y-branching devices or contactless couplers are presented with respect to possible embodiments of the branching device at the input and with respect to the 2.times.2 coupler at the output.
The difference of the optical path length in curved waveguides compared to straight waveguides in connection with an arrangement according to that disclosed in the above-mentioned European patent publication 0,482,461 is described in the paper of A. Tervonen et al, "Channel waveguide Mach-Zehnder interferometer for wavelength splitting and combining", Conference on Microoptics ECO, Hague, March 1991.
U.S. Pat. No. 4,515,430 shows (FIG. 2) and describes a Mach-Zehnder interferometer having a Y-branch at the input and two Y-branches at the output with two output waveguides. This arrangement is, however, a sensor, for example, for temperature. One arm is connected at both ends via narrow S-curves to the couplers and between the couplers, the other arm follows a large arc. The influence of bends on the optical path length is not described. Instead, the attenuation losses are minimized because of the configuration of the two arms.